Growth optimization and applicability of thick on-axis SiC layers using sublimation epitaxy in vacuum

Abstract

We demonstrate growth of thick SiC layers (100–200µm) on nominally on-axis hexagonal substrates using sublimation epitaxy in vacuum (10−5mbar) at temperatures varying from 1700 to 1975°C with growth rates up to 270µm/h and 70µm/h for 6H- and 4H–SiC, respectively. The stability of hexagonal polytypes are related to process growth parameters and temperature profile which can be engineered using different thermal insulation materials and adjustment of the induction coil position with respect to the graphite crucible. We show that there exists a range of growth rates for which single-hexagonal polytype free of foreign polytype inclusions can be maintained. Further on, foreign polytypes like 3C–SiC can be stabilized by moving out of the process window. The applicability of on-axis growth is demonstrated by growing a 200µm thick homoepitaxial 6H–SiC layer co-doped with nitrogen and boron in a range of 1018cm−3 at a growth rate of about 270µm/h. Such layers are of interest as a near UV to visible light converters in a monolithic white light emitting diode concept, where subsequent nitride-stack growth benefits from the on-axis orientation of the SiC layer.